Ascent

At T-3 minutes 45 seconds Paul Donnelly, the Launch Operations Manager in the Launch Control Center, wished the Apollo 11 crew, ''Good luck, and Godspeed.''

By T-2 minutes the 'boil off of liquid oxygen had ceased, and pressurisation was underway in all three stages of the launch vehicle. With one minute remaining on the clock, Armstrong reported, ''It's been a real smooth countdown." Ten seconds later, the launch vehicle went onto full internal power. Because the apparatus was much too complex for the final phase of the preparations to be managed manually, at T-20 seconds an automatic sequencer took over. At T-17 seconds, the guidance system in the Instrument Unit was released. The phased ignition sequence for the five F-1 engines was initiated at T-8.9 seconds, with the vehicle being held down by four clamps. Knowing that no Saturn V had lit its engines and then not lifted off, the astronauts turned their heads in their 'bubble' helmets and grinned at each other -they were going to fly! Jack King, the Public Affairs Officer at the Cape, counted down the remaining seconds, ''3, 2, 1,0. All engines running. Liftoff! We have a liftoff at 32 minutes past the hour. Liftoff on Apollo 11.''

As the clock ran down through its final minute, Joan Aldrin had sat stiffly in a chair, close to tears, fidgeting nervously with a cigarette, twisting a handkerchief, flexing her hands. She watched in silence as the vehicle lifted off. Although in a room full of children, relatives and neighbours, she managed to capture a sense of solitude. In fact, everyone in the room was silent. In contrast, Pat Collins had been very focused, discussing aspects of the flight plan with Barbara Young, who had been through this on Apollo 10. At liftoff, Pat called out delightedly, ''There it goes!''

As the vehicle began to rise from the pad, a plug drawn from its tail started the master event timer in the spacecraft. NASA specified the timing of mission events in terms of Ground Elapsed Time (GET), as measured from 'Range Zero', defined as the last integral second prior to liftoff - in this case 09:32:00 Eastern Daylight Time on 16 July 1969. Armstrong's heart rate was 110 beats per minute, Collins's 99 and Aldrin's only 88, in each case significantly lower than at this point in their Gemini flights. The first 12 seconds of a Saturn V launch were challenging, since the vehicle had to 'side step' away from the Launch Umbilical Tower, just in case a gust of wind pushed it towards the tower or one of the swing arms was tardy in rotating clear. As the vehicle gimballed its four outer engines to make this manoeuvre, it swayed this way and that; the effect being most pronounced at the top. As Collins observed later, ''It was, I thought, quite a rough ride in the first 15 seconds or so. I don't mean the engines were rough, and I don't mean it was noisy, but it was very busy - that's the best word for it; it was steering like crazy.'' Once the vehicle had cleared the 400-foot-tall tower, operational control was handed to Houston. The Instrument Unit of the Saturn V now commanded an axial roll in order to align the vehicle with the flight azimuth. Armstrong was to report key events to Houston, and at an elapsed time of T+ 13 seconds he called, ''We've got a roll program.'' This was acknowledged by Bruce McCandless, a yet-to-fly astronaut serving as the Capsule Communicator (CapCom). Between T+13.2 and T + 31.1 seconds, the vehicle rolled from a pad azimuth of 90°E to a flight azimuth of 72°E. Once aligned, the vehicle started to pitch over in order to arc out over the Atlantic on the desired ground track. ''Roll is complete,'' called Armstrong, ''and the pitch is programmed.''

Apollo 11 lifts off.
The F-1 engines of the 363-foot-long vehicle issue a tremendous exhaust plume.

For the crowds, the first indication that a launch was in progress was a light at the base of the vehicle. A jet of flame passed through a hole in the Mobile Launch Platform to a wedge-shaped deflector, which split and vented it horizontally north and south. Water had been pumped onto the pad to diminish the acoustic reflection from the concrete, and the water in the pit was vaporised and blasted out with the flame as a roiling white cloud. The space vehicle weighed 6.5 million pounds, 90 per cent of which was propellant. It was almost inconceivable that it could be raised off the ground, but the five F-1 engines, drawing propellants at the combined rate of 15 tons per second, yielded a total of 7.5 million pounds of thrust. As the vehicle slowly rose from the pad, exposing the flame, the intensity of the light rivalled the early morning Sun sufficiently to force observers not wearing sunglasses to squint their eyes. In the press stand, positioned some 3.5 miles from the pad because this was calculated to be as far as an exploding Saturn V could shoot a 100-pound fragment, some of the photographers, their cameras forgotten, simply stood and yelled 'Go!' again and again. No launch since John Glenn's had released such raw emotion in the press. At first it was like watching a silent movie, because the thunderous roar of ignition took 15 seconds to reach the official viewing sites. As the vehicle rose, the roar was overwhelmed by a staccato pop and crackle that was more felt than heard.6 The ground shook sufficiently to register on remote seismic sensors. To some observers, it was debatable whether the Saturn V was rising, or its great thrust was pushing the Earth aside! Dee O'Hara and Lola Morrow had been joined at the astronauts' viewing site by Beth Williams, wife of C.C. Williams, an astronaut who had been lost in an aircraft accident in 1967. Tears of joy streamed down their faces. On her boat 5 miles away, Jan Armstrong did not have a very good view, but she preferred reality to a television screen showing the narrow view from a long-range camera.

The main screen in front of the Mission Operations Control Room displayed a plot of the trajectory of the Saturn V, which was exactly as programmed. If it were to suffer a guidance failure, Armstrong was ready to steer it himself, and was the first commander to have this facility. The vehicle passed through the region of maximum dynamic pressure at an altitude of 4 nautical miles,7 while travelling at a speed of 2,195 feet per second. The slowly rising thrust from increasingly efficient engines, and the decreasing mass of the vehicle meant increasing acceleration. By design, the centre engine of the F-1 cluster shut down first to limit the acceleration. Once it had consumed some 4.5 million pounds of propellants, the S-IC was shut down. Its sustained thrust had compressed the vehicle lengthwise, and it snapped back to its true length when this force was suddenly removed, throwing the crew against their

6 The Saturn V was so much more powerful than its predecessors that the sound of the first launch on 9 November 1967 took everyone by surprise. It not only rattled the tin roof of the VIP bleacher but also threatened to collapse the booth from which Walter Cronkite was providing his television commentary.

7 NASA preferred to use nautical rather than statute miles for space missions. One nautical mile is 2,000 yards, or 6,000 feet; whereas a statute mile is only 1,760 yards or 5,280 feet.

harnesses; this 'eye-balls out' shock being particularly harsh immediately after the peak 'eye-balls in' load of 4 g.8 As the 138-foot-long spent stage was released by pyrotechnic charges on its upper rim, small solid rockets in the fairings around its tail fired to retard it. Other such rockets on the exterior of the interstage pushed the remainder of the vehicle clear and gave ullage to settle the S-II's propellants prior to firing its five J-2 engines. Already on the edge of space, the S-II was to combine continuing to climb with building up horizontal velocity. The spent stage followed a ballistic arc, 357 nautical miles long, into the Atlantic. Although staging occurred at an altitude of 36 nautical miles and 50 nautical miles downrange, it was visible to viewers at the Cape through thin high-level cloud.

The S-II was rather quieter than the first stage, built up its g-load gently, and ran smoothly. The role of the interstage was to prevent the discarded S-IC stage from coming into contact with the engines of the second stage. However, because it represented 'dead weight', it was promptly jettisoned. If it had been necessary to abandon the launch vehicle, the launch escape system would have been fired to draw the command module clear. The main solid rocket motor had a thrust of 150,000 pounds, which was fully twice that of the Redstone missile that fired Al Shepard on his suborbital Mercury mission. At an altitude of 60 nautical miles the escape system was jettisoned by firing a secondary solid rocket motor. The tower took with it the conical cover that had protected the command module during the ascent through the atmosphere and, if an abort had been made, would have protected it from the escape rocket's exhaust. Up to this point, all windows except that in the hatch had been masked. With all five windows uncovered, the cabin brightened markedly.9 As it was above the bulk of the atmosphere, the S-II could manoeuvre without enduring significant aerodynamic stress. It was tasked with correcting any trajectory errors inherited from the first stage. As with the S-IC, the middle engine was shut down first. On fuel depletion, the outer engines cut off. One second later, at an altitude of 101 nautical miles, 875 nautical miles from the Cape and far beyond the range of the television cameras, the S-II was jettisoned to fall into the Atlantic. Joan Aldrin, who had fidgeted throughout, now went into her bedroom to check the abbreviated flight plan that she had pinned on the wall.

On igniting its single J-2 engine, the S-IVB continued to navigate towards the 'keyhole in the sky' for orbit. As it pitched over, it presented the astronauts with a view of the curved horizon across the Atlantic; however, being veterans, they had seen it before. At a downrange distance of 1,461 nautical miles, the Instrument Unit of the vehicle noted that it had attained the required combination of altitude and

8 A load of 1 g corresponds to an acceleration of 32.2 feet per second per second.

9 The cabin had five windows, numbered 1 to 5 running left to right: outboard of the left couch, in front of that couch, in the main hatch by the centre couch, in front of the right couch and outboard of that couch, with the side windows being large and rectangular, the hatch window being circular and the forward-looking windows being small and wedge-shaped.

MERCURY^ I»""' IMJiCTION

MERCURY^ I»""' IMJiCTION

Was this article helpful?

0 0

Post a comment